Okay, maybe I am missing something here. They said they do not have a phone to sell you on the Next program because they are only selling to those who pre-ordered online. Those phones are meant for pre-orders and not walk-ins, so why would you not understand that they cannot sell one to you as a walk-in?
But then you cannot do Next on Apple.com, right? So your best bet would have been to walk outside, order one from your current smart phone under a 2-year contract, and go get it. If you can switch to Next from there, then great. I am unsure of the contract details of Next and switching from a traditional contract.
The problem really is that stock is low and this Apple store, if not all, are reserving phones for those who ordered online. I don't know that I see an issue with this at all. You're looking to get the phone for basically nothing out of pocket up front. If you want to do that then you must be patient and order online with AT&T. It sounds like that is really your only option. Unless I am missing something here and Apple.com allows orders for phones via the AT&T Next program.
Also, phone reps may not be aware of day to day operations inside Apple stores. Again, unsure of the policy of not selling to walk-ins throughout all Apple retail stores. It would be good to know, I suppose. You cannot completely blame the phone rep for sending you to the store though. Not completely. You should have called the store itself after being told to go to the store. Finally, I've never called an Apple retail store and got transferred to some call center, never. Not during launches of new products or mundane days where there was nothing new on the shelves.